This invention relates to reusable containers and more specifically to reusable containers formed of plastic materials.
In the past multi-purpose reusable containers have been formed of plastic materials by, for example, a conventionally known rotational molding process. Such containers were designed to withstand temperature extremes ranging from -40.degree. F. to +140.degree. F., and be resistant to water, vibrations and severe impacts. An example of one such prior art reusable container is illustrated in FIGS. 1-3. As illustrated in these figures, the reusable container includes a base member 11 which has hollow sidewalls. The hollow sidewalls include an outside portion 13 and an inside portion 15 which are joined at the top of the base member in a raised tongue portion 17. The container also includes a lid member 19 having an outside wall portion 21 and an inside wall portion 23. The inside and outside wall portions 21 and 23, respectively, are joined to one another at the bottom of the lid in a grooved portion 25. The lid member 19 fits over the base member 11 such that the respective tongue and grooves mate. A gasket is positioned in the groove 25 to thereby provide a water tight fit between the lid and base. The lid and base are secured to one another by means of a set of metallic locks 27 of known design.
With this prior art rotationally molded container, the tongue and groove arrangement serves only to align the lid and base and to provide a seal for the container. Stresses normally encountered by the container when dropped or impacted are too great to maintain registration and support between the lid and base member and accordingly in the prior art container metallic shear stops support 29 were positioned at each corner of the lid 19. The shear stops were secured to the lid by means of rivets 31 as illustrated in FIGS. 1 and 3. As best illustrated in FIG. 1, the shear stops 29 extended downwardly past the top of the base member 11 to provide lateral support under impact to thereby prevent the lid from shifting off the base member 11 and shearing the locks 27.
This arrangement has a number of drawbacks. For example, in the process of making the reusable container, extra labor and materials were required which resulted in increased cost and decreased reliability of the container. The metallic shear stop supports and the plastic material forming the container were thermally dissimilar and accordingly under severe temperature extremes, unacceptable stress concentration was generated in the corners of the container particularly when the container was impacted. This caused the plastic and even the gasket material to be damaged. In addition, the shear stop supports took up space inside of the container and required a relief cut in the corners of the cushioning materials positioned within the container. Finally, while the shear stop supports can only be positioned at the four corners of the container, large containers for supporting large and heavy equipment often require greater support than is available from the four corner shear stop supports. Therefore, this prior art arrangement has proven to be less than satisfactory.
It accordingly is an object of this invention to provide an improved, reusable container.